1. Field of the Invention
The present invention relates to a multi remote control system which is able to remotely control a plurality of electronic devices, and particularly to a remote control system which is able to select an operation target comfortably without interference even in an environment in which a plurality of device identification apparatuses exists.
2. Description of the Related Art
In recent years, a lot of electronic devices which are operable by a remote controller have been widely used at home, and a plurality of remote controllers often exists in the same room. Therefore, when a desired device is intended to be operated by a remote controller, other remote controllers may interfere with the remote controller or it may take time to search for the remote controller.
In order to solve the problem, products such as a learning remote controller and a multi-remote controller only by which functions of a plurality of remote controllers are provided are commercially available.
However, they have such a problem that it is necessary to manually resister functions to be used in advance, which takes a lot of trouble, that only determined functions are usable and a remote control function of a new electronic device cannot be added, or that there are many buttons, which causes difficulty in operation.
In order to deal with that, such a technique is proposed that a device identification code signal is transmitted from a device identification apparatus provided in an electronic device so as to modify the remote controller to have a function to operate the device.
FIG. 5 is an internal block diagram of a conventional device identification apparatus. The device identification apparatus is constituted by an infrared receiving section 101, a signal decryption section 102, and an infrared transmitting section 105. The infrared receiving section 101 receives a device selecting signal from a remote controller via infrared, and passes a code signal included therein to the signal decryption section 102. The signal decryption section 102 decrypts a meaning of the code signal, and if it is a device selecting signal from the remote controller, the signal decryption section 102 requests the infrared transmitting section 105 to transmit a device identification code signal. The infrared transmitting section 105 transmits a device identification code signal to the remote controller via infrared.
Here, the following deals with interference measures in a case where a plurality of electronic devices to each of which a device identification apparatus is attached are provided at a short distance and a device selecting signal from the remote controller reaches the plurality of device identification apparatuses at the same time.
For the device identification apparatuses, respective carriers for transmitting a device identification code signal are set to frequencies different from each other. The remote controller is provided with a band-pass filter so as to receive infrared signals having different carrier frequencies. The device identification apparatuses and the remote controller are configured in this way so as to transmit and receive infrared signals, thereby preventing interference.
The remote controller may further include a comparison circuit, so that it is also possible to select a device of a signal having a highest intensity by comparing intensities of received infrared signals (see, for example, Patent Document 1).
[Patent Document 1] Japanese Patent Application Laid-Open No. 7-123479